Indique o numero da pagina a remover:
<?php mn_field('text', 'ED', 'doc_page_number', '', '3', '3', '', ''); ?>
<?php mn_field('button', 'ED', 'doc_pagedel_submit', 'Remover', '', '', '', '" onClick="
    if(doc_page_number.value > 0) {
        if(confirm(\'Deseja mesmo apagar esta pagina \'+doc_page_number.value+\' deste documento?\')==true) {
            replaceUrl(\'doc_page_action\',\'_response/call.php?get=senderdocumentattch&ID=' . $_GET['ID'] . '&RSID=' . $_GET['RSID'] . '&RSIF=' . $_GET['RSIF'] . '&pag=\'+doc_page_number.value);
        }
    }'); ?>
<div id="doc_page_action"></div>